by In his first Just a few months into operation, the James Webb Space Telescope (JWST) is already proving that it was worth the wait! To date, it has provided astronomers with the most detailed and accurate images of the universe, made observations of iconic galaxies and nebulae, peered to the edge of the Universe and obtained spectra from distant exoplanets. These resulting images, released through the JWST Early Release Science (ERS) program, provided a good cross-section of what this next-generation observatory can do.
Among its many goals, JWST will provide valuable insights into the formation and evolution of exoplanet systems through direct imaging. Using data from ERS, an international team of astronomers and astrophysicists conducted a direct imaging study of a brown dwarf companion (VHS 1256-1257 b) orbiting a triple brown dwarf system, about 69.0 light-years away. The spectra obtained from this body provided a detailed composition of its atmosphere, which included an unexpected find – clouds of silicate minerals (aka sand)!
The research was conducted by the JWST Early Release Science Program for Direct Observations of Exoplanetary Systems (ERS 1386 team, for short) collaboration, led by the University of California Santa Cruz (UCSC). The paper describing their findings is the second in a series looking at direct observations of exoplanets made by Webb, both of which are currently under review. The first paper (released at the same time) looked at ERS data for the exoplanet HIP 65426 b, a super Jupiter observed by Webb in the near and mid-infrared wavelengths.
The ERS 1386 collaboration includes 120 astronomers from more than 100 institutes and universities worldwide and is dedicated to direct imaging of exoplanet systems in the mid-infrared range. This will include taking spectra of exoplanet atmospheres to determine habitability and examining disks around stellar debris to learn more about planet formation.
As the team stated during the 2018 European Planetary Science Conference, “humanity has never observed exoplanetary systems at these wavelengths, and our observations will be transformative for understanding the chemistry and compositions of these distant worlds.”
Technically, the program’s Early Release Program is designed to evaluate the performance of JWST’s observational modes that enable direct imaging of exoplanets, planetary mass companions, and the circumstellar disks that form them.
This includes the Near-Infrared Camera (NIRCam) and Mid-Infrared Instrument (MIRI) coronagraph modes (which blocks out starlight so exoplanets can be seen) and the Near Infrared Imager and Slitless Spectrograph (NIRSpec) aperture masking interference mode ) (which combines light from different sources to create images).
Dr. Aarynn Carter, a Postdoctoral Fellow at UCSC and member of ERS 1386, was the lead author of the collaboration’s first paper. As he explained to Universe Today via email, Webb’s observations of HIP 65426 b effectively demonstrated the observatory’s direct imaging capabilities:
“These observations showed that JWST is capable of obtaining accurate exoplanet flux measurements throughout the near-mid-infrared. These measurements allow us to obtain a precise constraint on the total emitted energy or luminosity of HIP 65426b. Compared to models of planetary evolution, this, in turn, gave us very precise constraints on the bulk’s properties, such as temperature, mass and radius. With future work, we can begin to understand what these observations mean for the atmospheric properties of HIP 65426 b.
For their latest study, the team consulted data obtained by Webb’s MIRI and NIRSpec of VHS 1256 b, a brown dwarf companion twenty times the mass of Jupiter and orbiting at a distance of about 150 AU. These observations were conducted on July 5, 2022, for more than two hours and at wavelengths ranging from 1 to 20 micrometers. The spectra they obtained provided detailed information on the atmospheric composition of VHS 1256 b and at wavelengths never before seen with a brown dwarf.
Dr. Britanny E. Miles, UC Irvine Chair Postdoctoral Fellow and member of the ERS 1386 Collaboration, was the lead author of the second paper. As he told Universe Today via email:
“The near-infrared and mid-infrared show characteristics of methane, carbon monoxide, sodium, potassium and water. There are signs of carbon dioxide. All of these features have previously been observed in brown dwarfs of this temperature. We’ve never seen carbon monoxide in this much detail at 5 microns, though.
“These give us the opportunity in future studies to understand how much carbon and oxygen there is in the overall object, which gives an idea of how ‘metal-rich’ it is compared to its host star. “The composition of a brown dwarf can potentially provide insight into the ways in which the object may have formed.”
Miles and her colleagues also noted the direct detection of silicate clouds, making this the first time such a phenomenon has occurred for a planetary-mass companion. This and other recent spectroscopic examinations of brown dwarfs (such as a recent study based on Spitzer data) confirm that these substellar-mass objects generate enough heat to vaporize minerals. It also provides information on how planetary atmospheres work, particularly for planets that are closer in size and temperature to Earth.
These results were similar to previous observations of HR 8799 c, d and e, three exoplanets orbiting a K-type variable star about 133 light-years from Earth. These exoplanets range between about 7 and 9 solar masses, are probably brown dwarfs, and have similar spectra. However, JWST provided much greater resolution and imaging capability than previous observing campaigns, further validating the advanced observatory and its ability to image and characterize exoplanets directly. Carter said:
“We also determined that JWST is up to a factor of 10 more sensitive than expected in these observing modes. This means that we will easily be able to make this kind of observation on a larger number of known objects. Additionally, for some stars, we will be more sensitive than is currently possible from the ground, meaning we may be able to discover new planets as well. Notably, so far we have directly imaged only objects larger than Jupiter. JWST may allow us to detect Saturn or even Uranus/Neptune analogs.”
The richly detailed study of exoplanets is just another way of doing this Webb fulfills its scientific objectives. With advanced optics, coronagraphs and spectrometers, this next-generation observatory will confirm and characterize exoplanets like never before. This will allow astronomers to complete the exoplanet inventory, detect smaller rocky planets orbiting closer to their stars, and further constrain the planets’ habitability. With any luck, it may even reveal the first evidence of life beyond our Solar System.
This article was originally published on Universe today with Matt Williams. Read the original article here.
